Vanadium telluride VTe2: a novel cathode for rechargeable aluminum batteries and its performance optimization

Vanadium telluride VTe2 has been successfully synthesized via hydrothermal reaction and characterized for the first time as a cathode for rechargeable aluminum batteries. The electrochemical activity of VTe2 originates from the redox pairs Te4+/Te2- and V5+/V4+. VTe2 delivers a first discharge capacity of 275 mAh g-1 at 100 mA g-1 vs. an Al anode. The charge transport within VTe2 is based on interaction with AlCl4- anions, while the charge storage mechanism is dominated by surface-controlled processes at low voltages and by diffusion-controlled processes at high voltages. However, VTe2 suffers a rapid, drastic capacity loss and a short cycle life (<100 cycles) due to the corrosive chloroaluminate electrolyte, which dissolves the cathode active material upon charging and causes the shuttle effect. Ti3C2Tx MXene (forming a composite with VTe2) and CMK-3 mesoporous carbon (embedded onto the separators) are used as strategies to avoid the shuttle effect of soluble species towards the anode. This enables the reversibility of the redox reaction, allowing VTe2 to develop a sustained electrochemical activity. VTe2/Ti3C2Tx composite with CMK-3 modified separators shows improved electrochemical performance over as-prepared VTe2: 63 mAh g-1 after 300 cycles vs. 10 mAh g-1 after 75 cycles at 100 mA g-1.